Method for manufacturing a photovoltaic module by thermoforming a multilayer stack

Abstract

The invention relates to a method for manufacturing a photovoltaic module, the method comprising: i) placing a multilayer stack (1) between a mould (2) and a deformable membrane (3), the multilayer stack comprising, as components, a front face sheet comprising at least one polymer, a rear face sheet comprising at least one polymer, at least one intermediate sheet and at least one photovoltaic cell which are sandwiched between the front face sheet and the rear face sheet, ii) thermoforming the multilayer stack, the thermoforming comprising - applying a fluid pressure to the opposite face of the membrane from the multilayer stack, in order to shape the multilayer stack against the mould and the membrane, - heating the multilayer stack to a temperature suitable for bonding together the components of the multilayer stack so as to form the photovoltaic module, and - cooling the photovoltaic module and removing the fluid pressure.

Description

[0001] Description

[0002] Title: Manufacturing process of a photovoltaic module by thermoforming a multi-layer stack

[0003] The present invention relates to the manufacture of a photovoltaic module, in particular having a complex three-dimensional shape, in particular curved.

[0004] In order to best preserve undeveloped natural areas, it is necessary to integrate photovoltaic modules into existing areas, for example buildings, infrastructure, consumer goods and mobility (vehicles), when deploying a large number of photovoltaic modules.

[0005] However, these integrations require that the shape and mass of the photovoltaic modules be adapted to the support intended to carry them. It is also necessary, for each photovoltaic module, to guarantee performance and durability in accordance with current regulations and to reduce the corresponding environmental footprint to meet the "net zero carbon" objective by 2035.

[0006] Known photovoltaic modules generally comprise several photovoltaic cells, capable of converting a luminous flux into an electric current, which are encapsulated in a laminate.

[0007] The laminate typically includes:

[0008] - a front face intended to be positioned facing the solar radiation incident on the photovoltaic cells and which is defined by a thermally tempered glass plate, with a thickness greater than 2 mm, generally between 2.8 mm and 6 mm,

[0009] - a multi-layer back face, generally comprising polyvinyl fluoride, for example marketed under the name TEDLAR©,

[0010] - photovoltaic cells coated with two adhesion films, called encapsulation, generally made of ethylene-vinyl acetate, placed between the front and rear faces.

[0011] The photovoltaic module may also include an aluminum frame, which supports the laminate and a junction box that allows the integration of protection such as bypass diodes or MOSFETs or an electronic circuit. The junction box also allows several photovoltaic modules to be electrically connected to each other. However, the use of a thick tempered glass front panel is not compatible with applications where the lightness of the photovoltaic module is required.

[0012] To lighten the laminate, it may be considered to thin the tempered glass plate to a thickness of less than 2 mm, or to replace it with a polymeric sheet, made for example of PVDF, ETFE, ECTFE, or FEP, or with a sheet of a composite material based on glass fibers immersed in an epoxy resin.

[0013] The laminate is obtained by a hot rolling process at a temperature of approximately 150°C. However, the lamination process has several drawbacks. In particular, it requires that the heating and compression phase of the laminate and the subsequent cooling phase be carried out in different devices. In addition, controlling the cooling rate after lamination is difficult, which complicates the implementation of this process with thermoplastic polymers that can crystallize, become whitish, diffuse light more and have lower transparency during cooling. In addition, the heating of the laminate is generally carried out by means of an oil circuit whose flash point is at most 194°C. The hot rolling process therefore does not allow the shaping of polymer materials for which shaping temperatures above 180°C are necessary.Finally, the hot lamination process only allows the manufacture of flat-shaped photovoltaic modules.

[0014] Furthermore, to produce modules with complex three-dimensional shapes, in relief, and in particular with one or more curvatures, it is known to implement processes such as bag molding, autoclave molding, resin transfer molding, known by the acronym RTM molding, reaction injection molding, also known by the acronym RIM molding. However, these processes require long implementation times which makes them inefficient and industrially incompetitive.

[0015] There is therefore a need for a new method of manufacturing a photovoltaic module which overcomes, at least in part, the drawbacks of the prior art.

[0016] The invention relates to a method for manufacturing a photovoltaic module, the method comprising: i) placing a multilayer stack between a mold and a deformable membrane, the multilayer stack comprising, as components, a front face sheet comprising at least one polymer, a rear face sheet comprising at least one polymer, at least one intermediate sheet and at least one photovoltaic cell sandwiched between the front face sheet and the rear face sheet, ii) thermoforming the multilayer stack comprising

[0017] - applying fluid pressure to the face of the membrane opposite the multi-layer stack, to shape the multi-layer stack against the mold and the membrane,

[0018] - heating the multilayer stack to a temperature suitable for bonding together the components of the multilayer stack so as to form the photovoltaic module, and

[0019] - cooling of the photovoltaic module and removal of fluid pressure.

[0020] The method according to the invention makes it possible to manufacture a photovoltaic module having a relief shape, by applying uniform pressure to the multilayer stack. This avoids applying locally high stresses which could damage the photovoltaic cells. Furthermore, as will become apparent later, the method according to the invention makes it possible to use a wide variety of polymeric materials, for example PA, PC, PP, PET G or PMMA, in particular which require forming temperatures above 170°C. Finally, the implementation of the method makes it possible to reuse the mold and the membrane to manufacture several photovoltaic modules and the manufacturing time of a photovoltaic module is faster than with the bag molding, RIM molding and RTM molding methods of the prior art.

[0021] Devices comprising a mold and a membrane for implementing the thermoforming of parts are described for example in WO 2009 / 125079 A2, WO 2012 / 131112 A2 and WO 2013 / 190020 A1, incorporated by reference.

[0022] Unless otherwise stated, the pressures expressed in this description and in the claims are absolute.

[0023] The membrane is particularly capable of matching the shape of the face of the mold against which the multi-layer stack is pressed.

[0024] Preferably, the temperature of the mold is less than 50°C, preferably less than 30°C, prior to the placement of the multilayer stack between the mold and the membrane. Preferably, the method comprises evacuating, at a residual vacuum pressure less than or equal to 1000 Pa, the interior space delimited by the mold and the membrane and in which the multilayer stack is housed and, optionally, the space delimited by the face of the membrane on which the fluid pressure is applied. The evacuation makes it possible to evacuate the air and to prevent gas bubbles from being trapped between the components of the multilayer stack, and degrade the properties of the photovoltaic module by facilitating the penetration of moisture and / or by acting as a delamination initiation zone between the components.

[0025] Preferably, the residual vacuum pressure is less than or equal to 1000 Pa, preferably less than or equal to 300 Pa, or even less than or equal to 100 Pa.

[0026] Heating of the multi-layer stack may be initiated before or concurrently with or after evacuating the interior space.

[0027] Preferably, the residual vacuum pressure is reached before the temperature of the intermediate sheet is at least 90°C, or even at least 80°C. This allows the gas contained between the components of the multi-layer stack to be evacuated from the interior space before the intermediate sheet melts under the effect of its temperature. The temperature of the intermediate sheet is for example determined from a measurement carried out by means of a calibration multi-layer stack equipped with a thermocouple arranged in contact with the intermediate sheet and which has been subjected beforehand to step ii) of thermoforming, or from the result of a thermal modeling of the thermoforming of the multi-layer stack, for example by the finite element method.

[0028] Preferably, the residual vacuum pressure is reached while the fluid pressure applied to the membrane is less than or equal to 20 kPa, or even before the application of the fluid pressure to the membrane, in order to avoid the formation of gas bubbles trapped in the photovoltaic module and / or to reduce the risk of damage to the photovoltaic cell(s).

[0029] In particular, the vacuum time for lowering the pressure in the interior space from atmospheric pressure to the residual vacuum pressure may be less than 60 s, preferably less than 30 s.

[0030] Preferably, the method comprises heating at least the mold in order to raise the temperature of the multilayer stack. The heat from the mold is then transferred to the multilayer stack, in particular by radiation and / or conduction. Preferably, the heating of the mold is carried out by electromagnetic induction, which makes it possible to localize the heating at the interface between the mold and the multilayer stack and for the temperature of said interface to be substantially uniform. The difference between the temperature of the mold and the temperature of the multilayer stack at said interface is preferably less than or equal to 5°C, in absolute value.

[0031] Preferably, the heating of the mold comprises a temperature raising step, from the temperature of the mold when placing the multi-layer stack in place to a holding temperature followed by a holding step at the holding temperature.

[0032] The temperature rise step can be carried out at a rate between 1.8°C. 1 and 2.5°C.s' 1 .

[0033] The holding temperature may be greater than or equal to 170°C, or even greater than or equal to 180°C, or even greater than or equal to 200°C, or even greater than or equal to 220°C, or even greater than or equal to 250°C, or even greater than or equal to 280°C, or even greater than or equal to 300°C.

[0034] The duration of the holding step can be between 1 minute and 15 minutes, preferably between 8 minutes and 12 minutes, better between 3 minutes and 5 minutes.

[0035] Preferably, the fluid pressure is applied to the membrane after heating of the multilayer stack has been initiated, so as to limit the risk of damage or even rupture of the photovoltaic cells. Preferably, the application of the fluid pressure to the membrane is carried out after the mold temperature has reached the holding temperature.

[0036] The fluid pressure applied to the membrane is greater than or equal to atmospheric pressure. It is preferably greater than 100 kPa, preferably greater than 200 kPa. Preferably, it is greater than or equal to 300 kPa, or even greater than or equal to 400 kPa. Furthermore, it is preferably less than or equal to 2000 kPa, or even less than or equal to 700 kPa, or even less than or equal to 600 kPa.

[0037] Fluid pressure can be applied to the membrane for a period of time between 1 minute and 15 minutes, including between 3 minutes and 5 minutes.

[0038] The fluid used to apply the fluid pressure may be a liquid or a gas. Preferably, the fluid is a gas, for example air. Preferably, the photovoltaic mold is cooled between the membrane and the mold, and preferably in contact with the membrane and the mold. Advantageously, the heating of the multilayer stack, the application of the fluid pressure and the cooling of the module can thus be implemented within the same device. This makes the method according to the invention simpler to implement, said steps being carried out in one cycle, and more efficient than a lamination method of the prior art which requires different devices to heat and cool the photovoltaic module.

[0039] Preferably, the cooling of the photovoltaic module is initiated before the fluid pressure is released. This prevents the photovoltaic module from deforming during cooling, as it is not sufficiently constrained by the membrane.

[0040] Preferably, the method comprises cooling the mold in order to cool the photovoltaic module by heat exchange between the mold and the photovoltaic module. The mold is for example cooled by circulation of a heat transfer fluid, for example water, in contact with the mold. In particular, the cooling rate of the mold may be between 0.2 °C. 1 and 2°C. 1 , preferably between 0.4°C. 1 and 1.6°C. 1 , for example 1.5°C. 1 .

[0041] Preferably, the fluid pressure is maintained on the membrane during cooling of the photovoltaic module at least until the temperature of the intermediate sheet is less than or equal to 50°C, or even less than or equal to 30°C. In this way, it is ensured that the mechanical properties are sufficient in the photovoltaic module.

[0042] Breaking the vacuum in the interior space, i.e. returning to atmospheric pressure from the residual vacuum pressure, can be carried out at a speed greater than 100 kPa.s' 1 . Preferably, it is carried out at a speed between 0.8 kPa.s' 1 and 1.7 kPa.s' 1 .

[0043] Preferably, fluid pressure is maintained on the membrane during vacuum breaking.

[0044] The vacuum in the interior space may be broken during or after cooling of the photovoltaic module.

[0045] The duration of thermoforming step ii) may be between 1 minute and 15 minutes, preferably between 3 minutes and 5 minutes. After cooling, the method may include extracting the photovoltaic module from the interior space.

[0046] The front face sheet is intended, after obtaining the photovoltaic module, to be placed between the source of solar radiation and the photovoltaic cell.

[0047] Preferably, at least one of the sheets selected from the front face sheet and the back face sheet is a multilayer.

[0048] Preferably, at least one of the sheets selected from the front face sheet and the back face sheet comprises a thermoplastic polymer.

[0049] The thermoplastic polymer may have a melting temperature greater than or equal to 180°C.

[0050] The thermoplastic polymer is for example chosen from a polyolefin (TPO), an epoxy resin, polypropylene (PP), polycarbonate (PC), polymethyl methacrylate acrylic (PMMA), polyester terephthalate glycol (PET G), polyamide (PA), polyphenylene sulfide (PPS) and their mixtures.

[0051] For example :

[0052] - the thermoplastic polymer is a polyolefin and the mold is maintained at the holding temperature of at least 120°C, for example for less than 1 minute; or

[0053] - the thermoplastic polymer is an epoxy resin and the mold is maintained at the holding temperature of at least 190°C for example for approximately 3.5 minutes; or

[0054] - the thermoplastic polymer is a polypropylene and the mold is heated to the holding temperature of at least 225°C, for example for about 2 minutes; or

[0055] - the thermoplastic polymer is PA6 and the mold is heated to the holding temperature of at least 260°C, for example for about 2.5 minutes; or

[0056] - the thermoplastic polymer is PAI 1 or PA 12 and the mold is heated to the holding temperature of at least 290°C, for example for about 3 minutes; or

[0057] - the thermoplastic polymer is PPS and the mold is heated to the holding temperature of at least 315°C, for example for about 3.5 minutes.

[0058] Preferably, at least one of the sheets selected from the front face sheet and the back face sheet, preferably the back face sheet, comprises a composite material comprising reinforcing fibers dispersed in a matrix of a polymer, preferably the thermoplastic polymer described above, the composite material being for example a woven or non-woven fabric impregnated with the polymer. The reinforcing fibers may be carbon fibers, glass fibers or natural textile fibers.

[0059] In one embodiment, the method comprises manufacturing the back face sheet by thermoforming as described in step ii) of a multilayer structure. This makes it possible, for example, to prepare a multilayer stack having a relief shape.

[0060] The conditions for heating the multilayer structure, applying fluid pressure to the membrane, and cooling the backsheet may be the same as or different from the thermoforming conditions for the multilayer stack. For example, the backsheet and the multilayer stack may be heated to different temperatures.

[0061] The multi-layer structure may comprise several sheets, at least one of the sheets having been manufactured by thermoforming as described in step ii) of a multi-layer element.

[0062] Furthermore, the photovoltaic cell preferably comprises a semiconductor, in particular silicon. Alternatively, it may be an organic or perovskite or CIGS photovoltaic cell. For example, the photovoltaic cell may be of the PERC, TopCOn, HJT, Tandem, IBC or MWT type.

[0063] The multi-layer stack preferably comprises several photovoltaic cells, preferably arranged in a regular arrangement in at least one direction in a plane parallel to or coincident with the median plane of the multi-layer stack.

[0064] Furthermore, the multi-layer stack may have a flat or complex shape, in particular curved. In particular, the multi-layer stack may extend in one or more curved directions that are different from each other. It may have at least one surface having at least one protruding relief and / or at least one hollow relief.

[0065] According to a preferred embodiment, the multilayer stack comprises, or is even constituted by:

[0066] - the multi-layer back sheet which comprises a ply comprising different or identical sheets made of a woven or fabric of carbon fibers impregnated in a thermoplastic polymer,

[0067] - several intermediate sheets each made of a thermoplastic encapsulation film,

[0068] - several photovoltaic cells electrically connected to each other and each in contact with the intermediate sheets and sandwiched between the intermediate sheets,

[0069] - the front face sheet which comprises, or even consists of, a thermoplastic polymer.

[0070] The mold may include at least one protruding relief and / or at least one recessed relief against which the multi-layer stack comes into contact during thermoforming.

[0071] The mold can be shaped so that the shape of the photovoltaic module has at least one curvature.

[0072] The mold is preferably metallic, for example steel.

[0073] The invention can now be better understood by reading the detailed description which follows and the examples presented for illustrative and non-limiting purposes, and the attached drawing in which:

[0074] [Fig. 1] is a schematic and cross-sectional view of a mold, a membrane, a multilayer stack and the photovoltaic module obtained at different stages of an example of implementation of the method;

[0075] [Fig. 2] represents, as a function of time t, expressed in minutes, the evolution of the set temperature of the mold Te expressed in °C (left scale), of the pressure in the interior space Pi expressed in mbar and of the fluid pressure Pf applied to the membrane, expressed in bar (right scale);

[0076] [Fig. 3] represents the schematic evolution of the temperature T p of the multilayer stack in different positions depending on the thickness of the multilayer stack as a function of time t; and

[0077] [Fig. 4] and [Fig. 5] are photographs of examples of a back sheet and part of a multi-layer stack respectively prior to thermoforming.

[0078] Figure 1 schematically illustrates different stages of an example of implementation of the method according to the invention and Figures 2 and 3 show the evolution of different operating parameters of the method.

[0079] The method involves thermoforming a multilayer stack 1 using a mold 2 and a membrane 3. In step i), as illustrated in Figure 1 a), the multilayer stack is placed between the mold and the membrane. The mold temperature T c and / or the membrane temperature is preferably less than 50°C, preferably at room temperature.

[0080] Thermoforming of the multi-layer stack against the mold is then carried out in step ii).

[0081] The lateral edges 4 of the membrane are brought into contact with the mold, then the gas contained in the interior space 5 delimited by the interior face 6 of the membrane and the interior face 7 of the mold which are each opposite the multilayer stack 1, is sucked in as illustrated in figure 1 b).

[0082] The suction of said gas can be carried out by means of a pump through orifices which open out through the inner face of the mold.

[0083] The suction of the gas induces a vacuum c])o of the interior space 5. The vacuum can be carried out in two stages, as illustrated in Figure 2. The pressure in the interior space Pi can first be reduced from atmospheric pressure to an intermediate pressure Pint, for example 300 Pa (3 mbar), and then to a residual vacuum pressure P vr of 100 Pa (1 mbar).

[0084] A set temperature Tc is then applied to heat the mold. The heating of the mold includes a temperature increase phase c|) i, for example according to a linear ramp up to a temperature maintenance phase c]>2, for example at 170 °C as illustrated in Figure 2. A higher or lower set temperature can of course be applied depending on the melting temperature of the components. Furthermore, the set temperature Tc can be applied to the mold before the residual vacuum pressure is reached. The mold is preferably heated by electromagnetic induction.

[0085] The temperature of the multilayer stack Tp is higher near its faces in contact with the mold and the membrane than at the level of the intermediate sheet(s). As can be seen in Figure 3, in the example illustrated, it evolves substantially linearly with time, like the set temperature of the mold.

[0086] The fluid pressure Pf is applied gradually to the outer face 8 of the membrane opposite the multilayer stack, preferably as soon as the temperature of the intermediate sheet reaches 80°C. In the example illustrated, it is applied once the set temperature reaches the mold holding temperature, and is constant, approximately 350 kPa. Alternatively, a first intermediate fluid pressure level may be applied before applying the maximum value of the fluid pressure, in particular to reduce the risk of rupture of the photovoltaic cell(s) when heating the components.

[0087] The fluid pressure deforms the membrane, the inner face 6 of which comes into contact with the facing face 9 of the multi-layer stack. It thus deforms the multi-layer stack which comes into contact against the hollow 10 and protruding 11 reliefs of the inner face 7 of the mold, as illustrated in Figure 1 c).

[0088] The set temperature Te of the mold is maintained at the holding temperature for a suitable period, for example between 180°C and 260°C so that the sheets which form the multi-layer stack are irreversibly bonded to obtain the photovoltaic module.

[0089] The mold heating is then interrupted. As illustrated in Figure 2, the set temperature of the mold can be reduced linearly. The mold is cooled during a phase c])3, for example by circulating water. The fluid pressure is maintained on the membrane until the temperature of the intermediate sheet in the photovoltaic module is below 50 °C or even below 30 °C. The photovoltaic module can then be extracted from between the membrane and the mold (phase c])4).

[0090] Example

[0091] Below is detailed an example of the production of a multilayer stack and of the implementation of the method according to the invention for manufacturing a photovoltaic module.

[0092] The back sheet was first prepared by thermoforming a multi-layer structure between the mold and the membrane according to the steps described above.

[0093] The multi-layer structure was formed by superimposing the following layers on top of each other.

[0094] A first sheet was obtained from a blank consisting of three plies each formed of a non-woven carbon fiber with a surface mass of 300 g / m 2and pre-impregnated with polypropylene. The blank was shaped against the mold and the membrane by thermoforming according to the steps described above, with application of a fluid pressure of 700 kPa on the membrane, heating of the mold to a set temperature of 220 °C reached in 1 minute and 40 seconds, holding at the set temperature for 4 minutes and cooling of the mold for 1 minute and 30 seconds to a temperature of 30 °C. The fluid pressure was then removed and the first shaped sheet was extracted from between the mold and the membrane.

[0095] A second sheet was obtained from a blank consisting of a ply of carbon fiber fabric with a surface mass of 200 g / m 2and two polypropylene felts, each with a thickness of 45 μm, on either side of the fabric. A transparent polyolefin film with a thickness of between 25 μm and 60 μm (with a surface mass of between 23 and 55 g / m 2 ) was placed in contact with the inner face of the mold to improve subsequent adhesion between the back face sheet and the intermediate sheet. The blank was shaped against the mold and the membrane by thermoforming under the same operating conditions as the first sheet, except that the set temperature was 230 °C.

[0096] The backsheet, photographed in Figure 4, was then formed by stacking the first and second sheets on top of each other. The resulting multilayer structure was placed opposite the mold and the second sheet opposite the membrane. The multilayer structure was shaped against the mold and the membrane by thermoforming under the same operating conditions as the second sheet.

[0097] A multi-layer stack was then prepared by superimposing the following sheets in the following order:

[0098] - front face sheet made of polyethylene terephthalate film with a thickness of 0.28 mm,

[0099] - two intermediate sheets, each 600 μm thick, made of a thermoplastic encapsulant with a Young's modulus of 18 MPa,

[0100] - photovoltaic cells, each with a thickness of between 0.14 mm and 0.18 mm and electrically connected to each other by interconnection strips with a thickness of between 0.1 mm and 0.3 mm,

[0101] - an intermediate sheet with a thickness of 600 pm, made of a thermoplastic encapsulant having a Young's modulus of 18 MPa, and

[0102] - the back face sheet described above.

[0103] The multilayer stack, photographed in Figure 5, was placed between the mold and the membrane, with the front face sheet facing the inner side of the mold. The multilayer stack was shaped against the mold and the membrane by thermoforming according to the steps described above. The multilayer stack was first evacuated in the interior space to a residual vacuum pressure of less than 1 kPa for 3 minutes and 10 seconds. The mold was heated from approximately 30 °C to a set temperature of 170 °C for 1 minute and 17 seconds and then held at the set temperature for 5 minutes. A fluid pressure of 350 kPa was applied to the membrane 3 minutes and 10 seconds after the mold began heating. The mold was cooled for 1 minute and 30 seconds. The fluid pressure was then removed and the photovoltaic module thus fabricated was extracted from between the mold and the membrane.

[0104] As appears from reading the present description, the invention makes it possible to manufacture a conformable photovoltaic module having a complex three-dimensional shape. It also allows the use of thermoplastic polymers which cannot be implemented by a lamination process of the prior art. A photovoltaic panel with a low surface mass, less than 5 kg / m 2 and / or presenting an aesthetic appearance pleasing to the eye, for example due to specific colors chosen for thermoplastic polymers or due to an aesthetic effect provided by fiber materials, can thus be obtained.

Claims

Claims 1. A method of manufacturing a photovoltaic module, the method comprising: i) placing a multilayer stack (1) between a mold (2) and a deformable membrane (3), the multilayer stack comprising, as components, a front face sheet comprising at least one polymer, a rear face sheet comprising at least one polymer, at least one intermediate sheet and at least one photovoltaic cell sandwiched between the front face sheet and the rear face sheet, ii) thermoforming the multilayer stack comprising - applying fluid pressure to the face of the membrane opposite the multi-layer stack, to shape the multi-layer stack against the mold and the membrane, - heating the multilayer stack to a temperature suitable for bonding together the components of the multilayer stack so as to form the photovoltaic module, and - cooling the photovoltaic module between the mold and the membrane and removing the fluid pressure, the cooling of the photovoltaic module being initiated before removing the fluid pressure.

2. Method according to claim 1, the temperature of the mold being less than 50°C, preferably less than 30°C, prior to the placement of the multi-layer stack between the mold and the membrane.

3. Method according to any one of claims 1 and 2, comprising placing under vacuum, at a residual vacuum pressure less than or equal to 1000 Pa, the interior space delimited by the mold and the membrane and in which the multilayer stack is housed.

4. Method according to the preceding claim, the residual vacuum pressure being reached before the temperature of the intermediate sheet is at least 90°C, or even at least 80°C.

5. Method according to any one of claims 3 and 4, the residual vacuum pressure being reached while the fluid pressure applied to the membrane is less than or equal to 20 kPa, or even before the application of the fluid pressure to the membrane.

6. A method according to any preceding claim, wherein heating of the multi-layer stack is initiated before applying fluid pressure to the membrane.

7. Method according to any one of the preceding claims, comprising heating at least the mold, in particular by electromagnetic induction, in order to raise the temperature of the multi-layer stack.

8. A method according to any preceding claim, wherein the fluid pressure is applied to the membrane after heating of the multi-layer stack has been initiated.

9. Method according to the preceding claim, the heating of the mold comprising a step of raising the temperature, from the temperature of the mold when placing the multilayer stack in place up to a holding temperature followed by a step of maintaining at the holding temperature, the holding temperature preferably being greater than or equal to 170°C, or even greater than or equal to 180°C, or even greater than or equal to 200°C, or even greater than or equal to 220°C, or even greater than or equal to 250°C, or even greater than or equal to 280°C, or even greater than or equal to 300°C.

10. Method according to the preceding claim, the temperature raising step being carried out at a rate of between 1.8°C. 1 and 2.5°C. 1 .

11. Method according to any one of the preceding claims, the fluid pressure being maintained on the membrane during the cooling of the photovoltaic module at least until the temperature of the intermediate sheet is less than or equal to 50°C, or even less than or equal to 30°C.

12. Method according to any of the preceding claims, at least one of the sheets chosen from the front face sheet and the back face sheet being a multilayer.

13. Method according to any one of the preceding claims, at least one of the sheets chosen from the front face sheet and the back face sheet comprising a thermoplastic polymer, for example chosen from a polyolefin (TPO), an epoxy resin, polypropylene (PP), polycarbonate (PC), polymethyl methacrylate acrylic (PMMA), polyester terephthalate glycol (PET G), polyamide (PA), polyphenylene sulfide (PPS) and mixtures thereof.

14. Method according to any one of the preceding claims, at least one of the sheets chosen from the front face sheet and the back face sheet, preferably the back face sheet, comprising a composite material comprising reinforcing fibers dispersed in a matrix of a polymer, preferably a thermoplastic polymer chosen from a polyolefin (TPO), an epoxy resin, polypropylene (PP), polycarbonate (PC), polymethyl methacrylate acrylic (PMMA), polyester terephthalate glycol (PET G), polyamide (PA), polyphenylene sulfide (PPS) and mixtures thereof, the composite material being for example a woven or a non-woven fabric impregnated with the polymer.

Images